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Plumbing Details in Straw Bale Construction

You have likely heard me say this before, but it is worth saying again: keep your plumbing out of your bales. Of course, it’s not as simple as that when it comes to adding plumbing to a straw bale house. There are obviously more details to consider in order to ensure that the straw bale walls are not damaged by water infiltration. The good news is that there are a limited number of locations to consider in terms of potential water damage from plumbing in a straw bale home so managing the installation is easier than you may think. Let’s look at the major areas of concern and I’ll show you my preferred solution for each location.

Kitchen Sink: In most homes in the United States (and I imagine around the world) the kitchen sink is located on an exterior wall with a window above it. This certainly makes the task of washing dishes more enjoyable (the view) but it does pose some problems to the mantra “keep your plumbing out of your bales.” It’s easy to bring the water up through the floor and into the base cabinets, and it is equally as easy to drop the waste line down through the cabinet floor. What become the big issues are venting, which is typically run vertically through the wall and out of the roof, keeping the plaster flat and square enough for cabinets and counters, and the depth of the bale wall itself. Although vents don’t necessarily contain water, they can still cause problems in bale walls in certain situations (roof leaks that drip down the pipe for example) and are best kept out of the bales.

For some, the wall depth won’t matter, but for others it is uncomfortable. The reason being that anything placed on the window sill will be hard to reach and the window itself is hard to open because it is so far away. Keep in mind that standard cabinets are 24″ deep, then add the 18+ inches of wall depth and you can see what I mean. Having the window more accessible and the space behind the sink shallower is more convenient for most people. The need for square and flat walls is nowhere as prevalent in a bale house as behind the cabinetry. If the walls are wavy or out of square, the installation of the cabinets and counter will be more difficult, and in some situations, not even possible (depending on the material choices). All of these situations can be addressed with the same solution, a framed wall section behind the sink.

The framed out area allows you to run all of your plumbing separate from the bales, thus eliminating the risk of water damage. It also provides for a flat and square installation with lots of nailing space for hanging your cabinets. Finally, it can be framed out thinner than the surrounding bale walls so that the window is more accessible and the space behind the sink is more shallow, allowing for useable space that was otherwise out of reach.

If you believe that you can create a flat and square wall for the cabinets within the bales and plaster and the depth of the wall doesn’t bother you, then the easiest thing is to either wet vent the kitchen sink (running the vent down through the floor or cabinets and then up through an interior framed partition wall) or simply create a water isolation box for the vent line within the bales. Both of these approaches are faster than framing an entire section of wall; however, be sure to check with your codes about the legality of wet venting and always keep the overall project quality, timeline and budget in focus when making your decisions so that you can choose the best option for your kitchen sink.

Showers and Tubs: The most common design, especially when considering a second bathroom in a home, is to have a tub/shower unit at the end of a narrow bathroom. This places the wettest part of the entire house in direct contact with the bales. That’s not a very good idea. If you cannot redesign your bathroom to eliminate this situation, then I strongly recommend the use of water isolation walls on either side of the tub/shower unit as shown in the diagram (click to see a full size version). This creates a safe detail for the bathroom and also increases the floor space in the bathroom or can allow you to move an interior wall to increase general home square footage.

Hose Bibs in Exterior Walls: Most jurisdictions require at least one exterior hose bib (faucet) on the house and that the bib is installed in the walls of the house as opposed to in the ground outside of the house. This means that it will be installed directly into the bales unless you plan for something different. And plan you should. I find that the best and most effective way of isolating the hose bibs from the bales is to build water isolation boxes. They can be created to fit within the wall such that the surrounding bales simply install next to and on top of the boxes with little interruption. Furthermore, once the walls are plastered, the existence of the boxes will no longer be noticeable to anyone. In fact, the only way that you will know they are there is from memory and your photos (of course you will photo all of the details of your home construction for later use…right? Right.) Check out the diagram for the details of how the boxes are built. Once again, you can click on the diagram to make it bigger.

There are a ton of details that go into the construction of any home, and that list of details is bigger and certainly less common-place within a straw bale home than it is in conventional construction. Be sure to consider every detail you can think of before you start building. The time to address the details is during the design process. After all, making changes on paper is much easier and far less expensive than making them in the field. To get clear on what you should be considering, check out my book A Modern Look at Straw Bale Construction. It covers all of the information discussed here plus everything from foundations to wall and roof systems and all the construction details in between. No need for you to try and reinvent the straw bale wheel when all the details are laid out for you in a clear and descriptive manner.

9 Responses to Plumbing Details in Straw Bale Construction

Great information!!! As I was reading in your article about the kitchen window, I was thinking, is it possible to place the windows of a strawbale house on the inner side of the wall? So you don’t have such a large space between you and the window and your window sill is small or no window sill at all. I was just wondering if that is possible or maybe place a window on the inner and on the outer side of the wall?

Hi Jeanette. Placing a window on the interior face of the wall means that the large sill would be open to the elements, something I’m not crazy about. I have done it in the past on homes that have a large overhang protecting the wall (10′ porch), but would not recommend it on a standard wall where water might find its way onto the exterior sill. Adding an additional window on the exterior face would add a lot of expense to the house (doubling the window costs, both labor and materials) and would create a space in which convection would continually move air, removing any additional insulation value one might hope to achieve with the second window. I think it’s best to keep the windows to the exterior.

First off, LOVE your site. My husband and I go through phases where we really want to build a straw bale home (and we eventually will) but your site is SO HELPFUL. I am currently in an environmental biology class and in my lab I am doing a presentation on eco-living and sustainability. Your website is my number once source for information on all things straw bale!
Thank you and I cannot wait to blow the class’s mind!

Hi Andrew! Just wondering what you thought about air admittance valves? I know code might not allow them in all states, but it seems like it could be a easy solution to the kitchen sink venting problem. Thanks for all your hard work!

From the little I know of them, I like them. They are allowed in most areas in the States as long as there is at least one envelope piercing vent on each line to which the valve is attached. It could be up or down stream from the valve as I understand it. It could be a good solution if it is allowed in your particular area AND you are able to vent the specific run of pipe elsewhere to meet the code.